The present invention relates to a magnetic head for use in a magnetic disk apparatus and the like, a method of manufacturing the same, and a head suspension assembly using the magnetic head.
With the trend to a larger capacity and a smaller size of hard disk drives (HDD), heads are required to have a higher sensitivity and larger output. To meet this requirement, magnetic heads using magneto-resistive devices based on a variety of principles are now under development. For example, strenuous efforts have been made to improve characteristics of GMR (Giant Magneto-Resistive) head currently available on the market. On the other hand, intense development is under way for a tunnel magneto-resistive (TMR) head which can be expected to have a resistance changing ratio twice or more higher than the GMR head. The GMR head employs a giant magneto-resistive (GMR) device for a magneto-resistive device, while the TMR head employs a tunnel junction magneto-resistive device (TMR device) for a magneto-resistive device. In addition, a variety of types of magnetic heads are known in the GMR head and TMR head.
Any type of magnetic head which employs a magneto-resistive device comprises a base, and a laminate stacked on the base and including a magneto-resistive device. One surface of the base and an end face of the magneto-resistive device are in face of a magnetic recording medium directly or through a protection film such as a DLC (Diamond-Like-Carbon) film or the like. The surface of the protection film, if provided, forms an air bearing surface (ABS), while the surface of the base and the end face of the magneto-resistive device form the ABS when the protection film is not provided.
In a process of manufacturing the magnetic head described above, a structure including the base and laminate (generally, a bar cut from a wafer, on which a plurality of magnetic heads are arranged in a line (an aggregate of bar-shaped magnetic heads)) undergoes a polishing step for mechanically polishing a surface thereof on the ABS side. This polishing step plays an important role for exposing the end face of the magneto-resistive device on the ABS side for highly sensitively detecting a weak magnetic field from a magnetic recording medium, and simultaneously for defining the height of the magneto-resistive device in the vertical direction relative to the polished surface to provide a specified resistance.
Since the structure is polished using hard particles such as diamond, smear (metal pieces produced during the polishing) is produced on the end face of the laminate including the magneto-resistive device on the ABS side. This smear can form a current path which bypasses the magneto-resistive device. The current path thus formed causes a reduction in the sensitivity and output of the magneto-resistive device, and substantially disables the magneto-resistive device.
To solve this problem, JP-A-11-175927 corresponding to U.S. Pat. No. 6,174,736 discloses a technique for removing the smear by dry etching an end face of a TMR device after it has been mechanically polished. This smear removing technique collectively dry etches the overall end face of a laminate including the TMR device, as well as the overall end face of a substrate (corresponding to the base) which supports the laminate when the end face of the TMR device is dry etched.
Now, a method of manufacturing a magnetic head using the conventional smear removing technique mentioned above will be described with reference to FIGS. 41A, 41B, 41C. FIGS. 41A, 41B, 41C are explanatory diagrams schematically illustrating essential steps in the manufacturing method.
Referring first to FIG. 41A, a reference numeral 200 denotes a bar cut from a wafer as described above. The bar 200 comprises a base 201, and a laminate 202 stacked on the base 201. The laminate 202 includes a TMR device 203. The ABS side (lower side in the figure) of the bar 200 illustrated in FIG. 41A is mechanically polished. The polishing results in a step “a” between a lower surface 202a of the laminate 202 including a lower surface 203a of the TMR device 203 and a surface 201a of the base 201 close to a magnetic recording medium, as illustrated in FIG. 41B. The step “a” as illustrated is caused by a polishing rate of the base 201 lower than a polishing rate of the laminate 202 from the fact that the base 201 (generally made of Al2O3—TiC, SiC, or the like) is harder than the laminate 202 (made of a magnetic material such as NiFe, sendust, CoFeNi, or the like). The step “a” after polishing is on the order of 3 nm to 5 nm.
For removing smear produced by the polishing, the overall lower surface of the polished bar 200 as illustrated in FIG. 41B is collectively dry etched by parallel flat sputter etching using an Ar gas, ion beam etching using the Ar gas, ion milling using the Ar gas, or the like. Consequently, the step “a” is extended to approximately 10–20 nm, as illustrated in FIG. 41C. This is because in such dry etching, the base 201 is etched at a lower rate than the laminate 202, with a large ratio of the etching rate of the later to that of the former.
Conventionally, however, no attention has been paid to the fact that the step “a” is extended by the dry etching for removing smear. The step “a” having the size of as much as 10–20 nm would cause a failure in supporting the future trend of increasingly higher recording density. For improving more and more the recording density, the step “a” must be minimized to make a magnetic spacing (spacing between an end face of a magneto-resistive device close to a magnetic recording medium and a magnetic layer of the magnetic recording medium) as narrow as possible. These aspects similarly apply to a variety of other magnetic heads as well as the TMR head.
JP-A-11-175927 also discloses that an end face of a TMR device is dry etched by using a Cl-based, a F-based, and an O2 gas. However, the use of these gases results in the formation of an insensitive region (erosion, oxide films, and the like) on the surface of the TMR device, causing an unfavorable reduction in output when the recording density is higher.